July 2009


Kingston Fossil Plant

TVA accepts findings of independent engineering report

A long-evolving combination of conditions at Kingston Fossil Plant — including an unusual bottom layer of ash and silt, high water content of the ash, the increasing height of stored ash and sloping dikes built over wet ash — caused the spill of Dec. 22, 2008.



The findings and analysis were part of a comprehensive six-month report made public June 25 by AECOM, one of the nation’s leading geo-technical engineering firms. TVA commissioned the AECOM study in January 2009.

AECOM shared information with independent consulting engineers retained by the Tennessee Department of Environment & Conservation and TVA’s Office of Inspector General. These groups met several times to conduct workshops and review data as it was being collected and processed.

AECOM’s root cause analysis found that the combination of several rarely found conditions led to the Kingston ash spill.

“TVA accepts the detailed findings and associated analysis put forth by AECOM,” said TVA Chief Operating Officer Bill McCollum. “We are confident that AECOM conducted an in-depth study that identified what caused our storage pond to fail. TVA deeply regrets the spill of coal ash from our Kingston plant and is fully committed to restoring the community near the site and to seeing to the needs of our Roane County neighbors.”

In forming its conclusions, AECOM took hundreds of soil borings and numerous core samples, and performed extensive laboratory testing on the samples. The engineering firm also performed exploratory excavations; installed instrumentation; studied maps, photographs and surveys; analyzed debris from the coal-ash release; reviewed design records and drawings; and interviewed TVA engineers and site operations personnel.

AECOM’s complete report on the cause of the Kingston coal-ash storage pond breach and subsequent ash spill is available here.

“TVA will carefully consider the findings in the AECOM reports as we evaluate options for closing the failed dredge cell at Kingston,” McCollum said. “The combination of conditions and factors identified by AECOM that contributed to the failure at Kingston are unusual, and no other ash pond in the TVA system was built exactly like Kingston.”

TVA has retained the Stantec Inc. engineering firm to assess all of TVA’s other ash and coal-combustion byproduct impoundments to ensure that they are structurally sound, and that no failure could occur at any other TVA plant.